It’s becoming clear that if you’re not using SIP trunking for your wide-area IP-based communications, you are likely paying too much for telecommunications service.

SIP trunks can save you money every month by moving voice over IP (VoIP), unified communications (UC) and other IP-based traffic off of TDM-based services. And the savings can be significant, even 50 percent or more for long distance charges and monthly access line fees. In this post, we’ll examine some of the areas where the savings come from.

SIP Trunking Allows for Aggregation

With TDM based services such as ISDN PRI lines or T1 services, you’re actually paying for two different aspects of the service. One is the access line that comes into your building and physically connects the PBX to the carrier service. Another is the individual channels or trunks that are carried over that trunk. A PRI or T1 line carries 23 trunks (plus one for signaling).

Trunks may carry different fees depending on what it’s used for, whether local calls, long distance or toll-free calls. For local calls, you’ll likely pay a fixed monthly fee for unlimited calling while for long distance or toll free you’ll pay a few cents per minute, but no monthly fee.

SIP trunking reduces these charges in a number of ways. For one, you’ll need fewer of them because trunks can be centralized to one or a few locations – such as data centers, headquarters or regional offices – and shared among many other sites. A company whose footprint spans time zones, for example, can have its West Coast offices using SIP trunks later in the day when the East Coast folks have largely gone home. In short, you’ll decrease the ratio of trunks required per number of users.

What’s more, you don’t have to dedicate trunks to local, long distance or toll-free calls. Each trunk can be shared by any sort of IP traffic. In practice, companies typically find they need 35 to 50 percent fewer SIP trunks vs. comparable TDM trunks.

Another source of savings is the fact that SIP trunks can be added one at a time, not in chunks of 23 as with PRI or T1 lines. So you can buy only what you need, and limit excess, unused capacity.

SIP Trunking Eases Use of Existing Capacity for UC and VoIP

PRI and T1 lines may cost $450 to $600 per month. Using SIP trunking, you can move PBX traffic off of those lines and onto far less expensive carrier Ethernet and, for small sites, DSL services.

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In many cases, you’ll be able to use capacity that you are already paying for to handle data communications. You’ll have to check utilization rates but most companies will find they have at least some spare capacity they can dedicated to SIP trunks. And by making effective use of Class of Service (CoS) capabilities, which are supported across carrier MPLS networks, you can ensure delay sensitive traffic gets the priority it needs.

Even if you do need to add bandwidth, it costs far less to upgrade a carrier Ethernet line as compared to a PRI.

Save with On-net Calling

There’s also savings to be had beyond access charges. With SIP trunking, all of your voice calls and other UC traffic flow over your data network. Calls or sessions between internal corporate locations, therefore, ride only over your company’s own network, meaning they’re “on-net” calls. That means they aren’t subject to any per-minute charge or monthly trunk charges. That can result in big savings as Jabra found in this case study we recently wrote about. You pay for the SIP trunk access; that’s it.

If you’re using a hosted service for some of your voice or other UC applications, such as videoconferencing, you can often connect to the provider using a SIP trunk as well.

These are just a few of the ways that SIP trunking can save you real money. To learn more, and to see some examples of the ROI from real-world implementations, check out the e-book, “SIP Trunking for Dummies.”